Two-phase projectile with a distal compression chamber

ABSTRACT

A projectile having a proximal tube and distal tube is described. A piston that is formed with a vent covers the distal end of the proximal tube. The piston is inserted into an open proximal end of the distal tube to establish a compression chamber in the distal tube between the axially moveable piston and a closed distal tube end. A valve is positioned at the proximal end of the proximal tube to selectively pressurize a space in the proximal tube between the valve and piston. The space, in turn, is in fluid communication with the compression chamber through the vent formed in the piston. The vent is formed as a constriction allowing fluid to flow into the compression chamber during an initial pressurization, while allowing for pressure buildup in the compression chamber during the initial relative movement between the proximal and distal tubes that occurs immediately after projectile launch.

This application is a continuation-in-part of application Ser. No. 13/789,514, filed Mar. 7, 2013, which is currently pending. The contents of application Ser. No. 13/789,514 are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention pertains generally to man-powered devices for launching projectiles. More particularly, the present invention pertains to projectiles which transfer pneumatic energy to a payload, in flight, to increase the payload velocity, after the projectile has been launched. The present invention is generally, but not exclusively, useful for projectiles that convert the kinetic energy from a launched projectile into potential energy of a compressed gas inside the projectile, and then transfer this potential energy as kinetic energy to a payload in the projectile, for increased payload velocity after the initial launch.

BACKGROUND OF THE INVENTION

An important factor for evaluating the performance of a man-powered launcher is the velocity at which a projectile is released from the launcher. Regardless whether the projectile is an arrow, a bolt, or a shot cluster, and regardless whether the projectile is launched by either a vertical bow or a crossbow, the resultant projectile velocity is an important measure of the launcher's performance. In the event, the resultant projectile velocity will be a function of the amount of energy (i.e. the capacity to perform work) that can be stored in the launcher prior to projectile launch, and thereafter used to propel the projectile onto its flight path. For the specific case of a man-powered weapon, a contributing factor for performance is the physical ability of the user.

In general, energy can be classified as being either thermal energy, potential energy or kinetic energy. Of primary interest here are potential and kinetic energy. By definition, potential energy is the energy which is possessed by a body by virtue of its position or condition relative to other bodies. For example, an object weighing one pound, when positioned ten feet above a surface prior to being dropped onto the surface, will expend ten foot-pounds of energy when it impacts against the surface. In this example, by virtue of its position relative to the surface, the one pound object had a potential energy of ten foot-pounds. As another example of potential energy, a compressed gas has a potential energy for performing work as it is allowed to expand. On the other hand, unlike potential energy, kinetic energy is the energy (work capacity) that a body possesses by virtue of being in motion. Mathematically expressed, kinetic energy is a function of the velocity of the object. Specifically, a particle having a mass “m”, that is moving with a linear velocity “v”, has a kinetic energy that is mathematically expressed as “½ mv²”. As is well known, potential energy and kinetic energy are interchangeable.

In light of the above, it is an object of the present invention to provide a device and method for converting the potential energy of a launching device into the potential energy of a compressed gas inside the projectile during a launch of the projectile; and then transferring this potential energy to a payload for use as kinetic energy that will increase velocity of the payload after the initial launch. Another object of the present invention is to provide a device and method for launching a projectile to achieve an in-flight velocity that otherwise exceeds the capability of the launching device. Still another object of the present invention is to provide a device and method for launching projectiles with a pneumatically assisted operational velocity that is easy to use, is simple to implement and is comparatively cost effective.

SUMMARY OF THE INVENTION

In accordance with the present invention, a device and method are provided for launching a projectile from a man-powered device which will achieve an in-flight velocity that otherwise exceeds the capability of the launching device by itself. More specifically, in an energy transfer sequence, the potential energy that is initially established in the projectile launcher is converted into kinetic energy for the projectile as the projectile is launched onto its flight path. Next, the kinetic energy that is imparted to the projectile is then, at least in part, converted into potential energy by compressing gas in a chamber, inside the projectile. In turn, this potential energy is transferred to a payload, as the compressed gas is allowed to expand, for use as kinetic energy that will increase payload velocity after the initial launch. Note that this multistep energy conversion process occurs in a dynamic fashion, such that various steps of the process may overlap in time.

Structurally, a device for the present invention includes a first component that is tubular shaped and is formed with a lumen which defines an axis. Further, the first component has an open end and a closed end. Also included in the device of the present invention is a second component that is engaged with the first component to create an assembly. Specifically, this assembly establishes a gas-filled compression chamber in the lumen of the first component that is located between the second component and the closed end of the first component. Within this combination, the assembly allows for a substantially free axial movement of the second component back and forth in the compression chamber of the assembly. Further, depending on the embodiment of the present invention, a payload is selectively mounted on a component of the assembly. For the present invention, the payload may be either a conventional arrow (e.g. a broadhead) as used with a vertical bow (launcher), a bolt as used with a crossbow (launcher), or a shot cluster that may be adapted for use by either type launcher.

As envisioned for the present invention, a man-powered launcher will be used to generate an axially-directed driving force on one component of the assembly (projectile) in order to propel the projectile from the launcher and onto its flight path. A consequence of this driving force is to cause a relative movement between the first component and the second component. Recall, the second component is free to move within the lumen of the first component (i.e. it is free to move within the gas chamber of the assembly). In the event, this movement further compresses gas in the compression chamber to thereby increase potential energy in the compressed gas.

Once gas in the compression chamber has been compressed as much as possible, which occurs at or about the time when the driving force becomes zero, the gas then begins to expand. During this expansion, potential energy in the gas is converted to kinetic energy by equal and opposite forces to both the first and second components. This causes a resultant increase in the velocity of one component, and a resultant dissipation in the velocity of the other component; a combination of events that separates the payload from the assembly.

With the above in mind, the present invention envisions two different types of operational embodiments. In one, the payload is mounted on the second component, and the driving force is generated on the first component. In the other embodiment, the payload is mounted on the first component and the driving force is generated on the second component. In either embodiment, the mass of the proximal (i.e. aft) component (m_(p)) can be less than the mass of the distal (i.e. forward) component (m_(d)). For both embodiments, the driving force for launch is exerted against the proximal component.

For an operation of the present invention, a launcher is selected and is configured (i.e. armed) for launch. Stated differently, the launcher is configured to store potential energy. A projectile is then positioned on the launcher for launch. Upon firing the launcher, the potential energy that is stored in the launcher is converted to kinetic energy by way of the driving force that acts to propel the projectile from the launcher. Specifically, this driving force acts on the projectile and is directed to accelerate the projectile along an axial path that is defined by the projectile.

During the initial acceleration of the projectile by the driving force, a first kinetic energy is generated for the first component of the assembly, and a second kinetic energy is generated for the second component of the assembly. All of this happens for separate but interrelated reasons. Specifically, the different components of the assembly will preferably be of different mass, and they can have different velocities at launch (recall: kinetic energy equals ½ mv²). In more detail, the different velocities occur because, while the driving force acts directly on the first component to accelerate it along the flight path, the second component experiences no such direct force. Instead, the second component tends to remain at rest and is accelerated only by forces exerted on it by the gas which is compressed in the compression chamber.

Simultaneously, as kinetic energy is imparted to the first and second components of the assembly, a potential energy is stored within the gas in the gas-filled chamber of the assembly. Specifically, this increase in potential energy occurs because the second component moves toward the first component during the initial acceleration, and the gas is compressed between components as the gas chamber is diminished in size. At the end of the first component's initial acceleration, the gas has been compressed as much as possible and it has its highest potential energy.

After the initial acceleration of the projectile (i.e. when the driving force becomes zero), the potential energy of the gas is converted into kinetic energy and an expansion of the gas acts on both the first component and the second component. The result here is an additional acceleration of the second component and its payload for separation of the payload from the projectile (assembly), and by a deceleration of the remainder of the projectile.

In a particular embodiment of the present invention, a two-phase projectile having a distal compression chamber includes a proximal tube and distal tube. For this embodiment, the distal tube is formed with a lumen, defines an axis, and has an open proximal end and a closed distal end. In addition, for this embodiment, the proximal tube is formed with a lumen and has a proximal end and a distal end. Also, a piston covers the distal end of the proximal tube and the piston may be formed with a vent. To assemble the projectile, the piston and distal end of the proximal tube are inserted into the open proximal end of the distal tube. With this arrangement, the proximal tube is engaged with the distal tube to provide for a back and forth axial movement of the piston and proximal tube in the lumen of the distal tube. A consequence of this structural arrangement is that a compression chamber is established in the distal tube lumen between the axially moveable piston and the closed distal end of the distal tube.

Also for this embodiment of the present invention, a valve, such as a Schrader valve, is positioned at the proximal end of the proximal tube to selectively pressurize a space in the lumen of the proximal tube between the valve and the piston. With this cooperation of structure, the space inside the proximal tube is in fluid communication with the compression chamber, either through the vent formed in the piston, or through gas leakage around the piston.

For a two-phase projectile having the distal chamber embodiment, the vent is sized and/or configured as a constriction such that fluid is able to flow through the vent only at relatively low fluid flow rates. For example, the vent can include a small diameter hole (i.e. pinhole) extending through the wall of the piston or the piston so as to form an imperfect gas seal. These structures, although constricting, still allow fluid to flow (i.e. at low flow rates) from the space in the proximal tube and into the compression chamber during an initial pressurization of the projectile. On the other hand, a substantial back flow of gas from the compression chamber to the space in the proximal tube during launch of the projectile is restricted by the constriction. Because of this, pressure is allowed to build in the compression chamber during the initial relative movement between the proximal and distal tubes that occurs immediately after launch. As described above, this pressure buildup (potential energy) is subsequently imparted to the distal tube as kinetic energy, in flight, increasing the distal tube's velocity.

Also for this embodiment, a sleeve chamber is established between the inner surface of the distal tube and the outer surface of the proximal tube. In addition, the proximal tube is formed with an opening through its sidewall to establish fluid communication between the space in the proximal tube and the sleeve chamber. To seal the sleeve chamber, an O-ring is disposed between the inner surface of the distal tube and the outer surface of the proximal tube and a ramp shaped member is positioned in the sleeve chamber next to and distal to the O-ring.

During an initial pressurization of the projectile through the valve, the sleeve chamber becomes pressurized via the proximal tube opening. As the sleeve chamber becomes pressurized, the member moves axially to deform the O-ring and to increase a sealing force between the proximal tube and the O-ring, the inner surface of the distal tube, and the outer surface of the ramp shaped member. An annular ring is press-fitted into the open end of the distal tube. The friction force between the annular ring and the inner surface of the distal tube prevents the distal tube from separating from the proximal tube (due to pressure in the compression chamber) prior to launch. On the other hand, the pressure developed in the compression chamber during flight is sufficient, when converted to kinetic energy, to overcome the friction force, allowing separation of the proximal and distal tubes.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:

FIG. 1A is an elevation view of a projectile in accordance with the present invention, shown mounted on a vertical cross bow for launch;

FIG. 1B is a view of the projectile as shown in FIG. 1A with the projectile at the release point where it is launched from the launcher;

FIG. 1C is a view of the projectile as shown in FIGS. 1A and 1B with the payload in flight toward a target after the payload has separated from the remainder of the projectile;

FIG. 2 is a side view of a first preferred embodiment of a projectile in accordance with the present invention;

FIG. 3 is a side view of an alternate second preferred embodiment of a projectile in accordance with the present invention;

FIG. 4A is a cross section view of a first preferred embodiment of the projectile of the present invention as seen along the line 4-4 in FIG. 2, prior to a launch of the projectile;

FIG. 4B is a cross section view of the first preferred embodiment of the projectile as seen in FIG. 4A, at its release point, as it is being launched from the launcher;

FIG. 4C is a cross section view of the first preferred embodiment of the projectile as seen in FIGS. 4A and 4B, as the payload is about to be separated from the remainder of the projectile;

FIG. 5A is a cross section view of a second preferred embodiment of the projectile of the present invention as seen along the line 5-5 in FIG. 3, prior to a launch of the projectile;

FIG. 5B is a cross section view of the second preferred embodiment of the projectile as seen in FIG. 5A at its release point, as it is being launched from the launcher;

FIG. 5C is a cross section view of the second preferred embodiment of the projectile as seen in FIGS. 5A and 5B after a payload has been separated from the remainder of the projectile;

FIG. 6 is a cross section view of an embodiment of a two-phase projectile as seen along line 6-6 in FIG. 3 having a piston with a pinhole vent and a Schrader valve (shown in plan view for clarity);

FIG. 7A is a detail view as enclosed by line 7A-7A in FIG. 6 showing a portion of a sleeve compartment in a non-pressurized state;

FIG. 7B is a detail view as in FIG. 7A showing the sleeve compartment in a pressurized state in which a sealing force has been established between an O-ring, the outer surface of the annular ring and the inner surface of the distal tube;

FIG. 8A is a cross section view of another embodiment of a two-phase projectile as in FIG. 6 having a piston with a labyrinth vent passageway; and

FIG. 8B is a cross section view of another embodiment of a two-phase projectile as in FIG. 6 having a piston with a twin-O-ring seal and a pair of radial vents which serve to equalize the pressure around the proximal face of the outer O-ring.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to FIG. 1A, a device in accordance with the present invention is shown and is generally designated 10. As shown, the device 10 includes a projectile 12 and a man-powered launcher 14. In the particular case of the device 10 that is shown in FIG. 1A, the launcher 14 is a vertical bow of a type well known in the art. The launcher 14, however, could as well be a crossbow (not shown) or an air gun (not shown), both of which are of types well known in the pertinent art.

As illustrated sequentially in FIGS. 1A, 1B and 1C, a purpose of the present invention is to use the launcher 14 to propel the projectile 12 along a flight path (dashed line) 16 toward a target 18. In sequence, FIG. 1A shows the launcher 14 in a configuration for firing the projectile 12. FIG. 1B then shows the projectile 12 as it is being released from the launcher 14. And, FIG. 1C shows the projectile 12, and its payload 20 after it has been separated from the projectile 12 in flight, after launch. In particular, FIG. 1C shows that shortly after launch, the payload 20 continues along the flight path 16 toward the target 18, while the projectile 12, itself, falls to the ground along a separation path (dotted line) 22.

From an energy perspective, FIG. 1A shows a projectile 12 that is ready to be shot from a launcher (vertical bow) 14. In detail, the launcher 14 is configured to have a useable potential energy that can be converted into the kinetic energy of motion for the projectile 12. FIG. 1B on the other hand, shows the projectile 12 at its release point from the launcher 14, after the potential energy in the launcher (FIG. 1A) has been transferred to the projectile 12 as an internal mixture of potential energy and kinetic energy. In FIG. 1C, the payload 20 is shown after its separation from the projectile 12.

In terms of energy transfer, the separation of payload 20 from projectile 12 is caused when a portion of the kinetic energy in the projectile 12 (at launch, FIG. 1B) is pneumatically converted into potential energy of compression inside the projectile 12, and then reconverted into kinetic energy for the payload 20. With this reconverted kinetic energy, the velocity “v” of the payload 20 is increased sufficiently to separate the payload 20 from the projectile 12. Importantly, the payload 20 will substantially maintain the increased velocity “v”.

FIGS. 2 and 3, respectively, show two different embodiments for the present invention. In detail, FIG. 2 (with cross reference to FIGS. 4A-C) shows a projectile 12 which includes a proximal component 24 that defines an axis 26. For this embodiment of the present invention, a distal component 28 is positioned inside the proximal component 24 (see FIG. 4A). In another embodiment of the present invention, which is shown in FIG. 3, the distal component 28′ is positioned on the outside of the proximal component 24′. Both embodiments, respectively, include a nock 30 (30′) that is attached to the proximal component 24 (24′). Further, the embodiment for the device 12′ that is shown in FIG. 3 also includes a plurality of fletches 32 that are attached to the distal component 28′, and a plurality of fletches 34 that can be attached to the proximal component 24′.

With reference to FIG. 4A, it will be appreciated that the proximal component 24 is an elongated tube which is formed with a lumen 36 that extends along the length of the proximal component 24. The lumen 36 has an open end 37, and it has an arresting ring 38 which is located proximate the open end 37. At the other end of the proximal component 24, the nock 30 is affixed to the proximal component 24 to establish a closed end for the lumen 36. FIG. 4A also shows that the distal component 28 of the projectile 12 is a cartridge 40 which holds a payload 20. For the embodiment of the projectile 12 shown in FIGS. 4A-C, the payload 20 is a shot cluster. Further, the cartridge 40 is shown to include a stabilizing ring 42 and a sealing ring 44 that together maintain an axial alignment for the cartridge 40 as it moves back and forth along the axis 26 inside the lumen 36 of the proximal component 24.

Still referring to FIG. 4A, with the distal component 28 (i.e. cartridge 40) positioned inside the lumen 36 of the proximal component 24, it will be appreciated that a compression chamber 46 is established between the cartridge 40 and the nock 30 of the projectile 12. Importantly, the sealing ring 44 establishes a substantially air-tight seal for the compression chamber 46. On the other hand, as evidenced by cross reference with FIGS. 4B and 4C, the cartridge 40 must be allowed to freely move back and forth inside the lumen 36 of the proximal component 24. Stated differently, it is essential to the operation of the present invention that the compression chamber 46 be dimensionally variable.

FIGS. 5A-C show another embodiment of the present invention wherein a compression chamber 48 is established in the lumen 36′ of the distal component 28′ of the projectile 12′. Specifically, for this embodiment, a sealing ring 50 is provided on the proximal component 24′ that interacts inside the lumen 36′ with the distal component 28′. With this interaction, a compression chamber 48 is established between the components 24′ and 28′. As with the compression chamber 46 for the embodiment of the projectile 12 (see FIGS. 4A-C), it is essential to the operation of the projectile 12′ of the present invention that the proximal component 24′ move freely relative to the distal component 28′, and that the compression chamber 48 thereby also be dimensionally variable.

In an operation of the present invention, a driving force 52 (represented by the arrows 52 in FIGS. 4A and 5A) is applied to the projectile 12 (12′) by way of the nock 30 (30′). This occurs during a transformation of the launcher 14 between the consecutive configurations shown in FIG. 1A and FIG. 1B. As shown in FIGS. 4A-C, the effect of this driving force 52 on the projectile 12 is at least three-fold. For one (see FIGS. 1A and 1B), the projectile 12 will be accelerated to a launch velocity “v” for release from the launcher 14. Simultaneously, in a second effect (see FIGS. 4A and 4B), the relatively unrestrained distal component 28 (i.e. cartridge 40) is caused to move forward more slowly (i.e. toward nock 30), against the resistance of gas in the compression chamber 46. Thirdly, gas in the compression chamber 46 is compressed by the relative movement of the distal component 28 (cartridge 40) as the dimensions of the chamber 46 become smaller (see FIG. 4B).

After the projectile 12 has been launched from the launcher 14 (see FIG. 1B), the driving force 52 no longer acts to accelerate the projectile 12. Also, the potential energy that was generated by compressing gas in the compression chamber 46 reaches its maximum. As gas in the compression chamber 46 is then allowed to expand, its potential energy is converted into a kinetic energy that is manifested by an increased velocity for the cartridge 40, and its payload 20 and by a decreased velocity for the proximal component 24. This increasing difference in velocities then causes the payload 20 to separate from the cartridge 40 and to continue along the flight path 16 (see FIG. 1C). At the same time, as gas in the compression chamber 46 expands, the conversion of potential energy into kinetic energy is also manifested as a decrease in the velocity of the proximal component 24. As intended for the present invention, this decrease in velocity of the proximal component 24 will result in the proximal component 24 being launched at a substantially lower velocity than the payload. A special case involves component 24 falling (generally vertically) to the ground along the separation path 22 (see FIG. 1C).

A similar operational scenario occurs for the embodiment of projectile 12′ as shown in FIGS. 5A-C. More specifically, as evidenced by a comparison of FIG. 5A with FIG. 5B, the driving force 52 acts on the nock 30′ to accelerate the projectile 12′. This also compresses gas in the compression chamber 48 in the distal component 28′. In this case, however, the payload 20′ is mounted directly on the distal component 28′ and, thus, both the payload 20′ and distal component 28′ are separated from the proximal component 24′. In the event, expanding gas in the compression chamber 48 acts to increase the velocity of the distal component 28′ (payload 20′) and to diminish the velocity of the proximal component 24′.

FIG. 6 shows another embodiment of a projectile 12 a′ in accordance with the present invention. As shown, the projectile 12 a′ can include a proximal tube 54 and distal tube 56. For the projectile 12 a′, the distal tube 56 is formed with a lumen 58, defines an axis 60, and has an open proximal end 62 and a closed distal end 64. In addition, for the projectile 12 a′, the proximal tube 54 is formed with a lumen 66 and has a proximal end 68 and a distal end 70.

FIG. 6 also shows that a piston 72 covers the distal end 70 of the proximal tube 54 and is formed with a vent 74. When the projectile 12 a′ is assembled, the piston 72 and distal end 70 of the proximal tube 54 are inserted into the open proximal end 62 of the distal tube 56, as shown. With this arrangement, the proximal tube 54 is engaged with the distal tube 56 to provide for a back and forth axial movement of the piston 72 in the lumen 58 of the distal tube 56. As shown, this results in the establishment of a compression chamber 76 in the lumen 58 of the distal tube 56 between the axially moveable piston 72 and the closed distal end 64 of the distal tube 56.

Continuing with FIG. 6, it can be seen that a valve 78, which for the article shown is a so-called Schrader valve, is positioned in the lumen 66 at the proximal end 68 of the proximal tube 54. A nock (not shown) can be positioned in the lumen 66 at the proximal end 68 and positioned to extend proximally to the proximal tube 54. For the projectile 12 a′, a source (not shown) of compressed fluid, such as air, can be operably connected to the valve 78 which, in turn, can be employed to regulate the introduction of a filling gas into space 80 in the lumen 66 of the proximal tube 54 between the valve 78 and piston 74. As shown, the space 80 is in fluid communication with the compression chamber 76 through the vent 74 formed in the piston 72 allowing gas flowing through the valve 78 to reach and pressurize the compression chamber 76. For example, in a typical implementation, the space 80 and compression chamber 76 may be pre-pressurized to an initial gauge pressure in the range of about 70 to 90 psig, with a target of about 80 psig, prior to launch.

With continued reference to FIG. 6, it can be seen that an annular shaped sleeve chamber 82 is established between the inner surface 84 of the distal tube 56 and the outer surface 86 of the proximal tube 54. Axially, the sleeve chamber 82 extends from the friction ring 83 to the piston 72. The friction ring 83 is press-fitted into the open end of the distal tube 56. Also shown, the proximal tube 54 is formed with an opening 88 to establish fluid communication between the space 80 in the proximal tube 54 and the sleeve chamber 82.

As best seen in FIGS. 7A and 7B, an O-ring 90 is disposed between the inner surface 84 of the distal tube 56 and the outer surface 86 of the annular ring 92. Also, the annular ring 92 formed with a ramp surface 94 is positioned in the sleeve chamber 82. The annular ring 92 is permanently sealed to the proximal tube 54. Prior to initial pressurization (FIG. 7A), the O-ring 90 is on the ramp surface 94. During pressurization through the valve 78 (FIG. 6), the sleeve chamber 82 becomes pressurized via the proximal tube opening 88. As the sleeve chamber 82 becomes pressurized, the annular ring 92, together with the proximal tube 54, moves axially in the direction of arrow 96 to deform the O-ring 90 and compress the O-ring 90 between the inner surface 84 and the annular ring 92 as shown in FIG. 7B. When compressed as shown in FIG. 7B, a friction force is established between the O-ring 90, the inner surface 84 of the distal tube 56 and the outer surface 86 of the annular ring 92. The friction force between the friction ring 83 and the inner surface 86 of the proximal tube 54 prevents the distal tube 56 from separating from the proximal tube 54, due to pressure in the compression chamber 76 (FIG. 6), prior to launch. On the other hand, the pressure developed in the compression chamber 76 during flight is sufficient, when converted to kinetic energy, to overcome the friction force provided by the friction ring 83 (FIG. 7A), allowing separation of the proximal tube 54 and distal tube 56.

For this projectile 12 a′ shown in FIG. 6, the vent 74 is sized and/or configured as a constriction such that fluid is able to flow through the vent 74 only at relatively low fluid flow rates. As shown in FIG. 6, the vent 74 can be formed as a small diameter hole (i.e. pinhole) extending through the wall 98 of the piston 72 allowing fluid communication between the space 80 in the proximal tube 54 and the compression chamber 76.

In an alternative embodiment, as shown in FIG. 8A, the piston 72′ can include a vent 74′ formed as a labyrinth shaped passageway establishing fluid communication between the space 80′ in the proximal tube 54′ and the compression chamber 76′. More specifically, the labyrinth shaped vent 74′ connects the compression chamber 76′ with the sleeve chamber 82′, and the sleeve chamber 82′ connects with the space 80′ via the opening 88′, as shown.

The pinhole shaped vent 72 (FIG. 6) and labyrinth shaped vent 72′ (FIG. 8A), although constricting, still allow fluid to flow (i.e. at low flow rates) from the space 80, 80′ and into the compression chamber 76, 76′ during an initial pressurization. On the other hand, a substantial back flow of gas from the compression chamber 76, 76′ to the space 80, 80′ during launch of the projectile 12 a′ is prevented by the constriction. Because of this, pressure is allowed to build in the compression chamber 76, 76′ during the initial relative movement between the proximal tube 54, 54′ and distal tube 56, 56′ that occurs immediately after launch. This pressure buildup (potential energy) is subsequently imparted to the distal tube 56, 56′ as kinetic energy, in flight, increasing the velocity of the distal tube 56, 56′.

FIG. 8B shows another embodiment of a piston 72″ having an O-ring assembly which includes both an outer ring 100 and an inner ring 102. For purposes of the present invention, the outer ring 100 is preferably made of polytetrafluoroethylene (PTFE); more commonly known as Teflon®, a brand name of the DuPont Company. Further, the outer ring 100 can be formed with a diagonal split (not shown) that allows for very slight variations in contraction and expansion of the outer ring 100 during an operation of the projectile 12 a′ (FIG. 6). Also, as an integral part of the O-ring assembly, the inner ring 102 is preferably made of an elastomeric material (e.g. rubber) and it is positioned in the retention groove 104 with the outer ring 100, substantially as shown. Specifically, in this combination, the inner ring 102 is positioned to urge against the outer ring 100, to thereby force the outer ring 100 into direct contact with the inner surface 84″ of the distal tube 56″. This contact between the outer ring 100 and the distal tube 56″ will create a seal between the sleeve chamber 82″ and the compression chamber 76″. However, as envisioned for the present invention, in some implementations, leakage will occur between the piston 72″ and inner surface 84″ of distal tube 56″ (i.e. leakage past the outer ring 100). As a consequence, this leakage establishes fluid communication between the space 80″ in the proximal tube 54″ and the compression chamber 76″. More specifically, due to the leakage, the compression chamber 76″ is in fluid communication with the sleeve chamber 82″, and the sleeve chamber 82″ connects with the space 80″ via the opening 88″, as shown. With this arrangement, the compression chamber 76″ can be pre-pressurized by pressurizing the space 80″ (i.e. with gas introduced through valve 78 shown in FIG. 6). It is also important to note that the radial vent 106 in the retention groove 104 can be provided to equalize gas pressure in the compression chamber 76″ with gas pressure against the O-ring assembly (i.e. outer ring 100 and inner ring 102). Specifically, this is done to prevent the rapid build-up of pressure in the gas compression chamber 76″ during a launch from having an adverse effect on the O-ring assembly.

While the particular Two-Phase Projectile with a Distal Compression Chamber as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims. 

What is claimed is:
 1. A device which comprises: a distal tube formed with a lumen and defining an axis, and wherein the distal tube has an open proximal end and a closed distal end; a proximal tube formed with a lumen and having a proximal end and a distal end; the proximal tube engaged with the distal tube to provide for a back and forth axial movement of the proximal tube in the lumen of the distal tube; a piston covering the distal end of the proximal tube, wherein the piston is formed with a vent; a valve at the proximal end of the proximal tube to selectively pressurize a space in the lumen of the proximal tube between the valve and piston, the space being in fluid communication with the distal tube lumen through the vent to establish a compression chamber therein between the piston and the closed distal end of the distal tube; and a launcher for generating an axially-directed driving force on the proximal tube to propel the proximal tube onto a flight path in the axial direction with an initial relative movement between the proximal and distal tubes to compress gas in the compression chamber and generate potential energy in the compressed gas for use in separating the proximal and distal tubes in flight.
 2. A device as recited in claim 1 wherein the piston further comprises an O-ring assembly positioned in a retention groove formed in the piston to establish a seal between the piston and the distal tube.
 3. A device as recited in claim 2 wherein the retention groove is formed with at least one vent hole to establish fluid communication for equalizing pressure between the retention groove and the compression chamber, and wherein the O-ring assembly comprises: an outer ring positioned in the retention groove for contact with the distal tube; and an inner ring positioned in the retention groove to produce a force against the outer ring to urge the outer ring into contact with the distal tube.
 4. A device as recited in claim 3 wherein the inner ring is made of rubber and the outer ring is made of polytetrafluoroethylene (PTFE), and further wherein the outer ring is formed with a diagonal split to permit contraction and expansion of the outer ring.
 5. A device as recited in claim 1 wherein the piston is formed with a wall and the vent comprises a hole extending through the wall of the piston.
 6. A device as recited in claim 1 wherein the valve is a Schrader valve positioned in the proximal tube lumen.
 7. A device as recited in claim 1 wherein the proximal tube has an outer surface, the distal tube has an inner surface and the proximal tube is engaged with the distal tube to establish a sleeve chamber between the inner surface of the distal tube and the outer surface of the proximal tube.
 8. A device as recited in claim 7 wherein the proximal tube is formed with an opening to establish fluid communication between the space in the proximal tube and the sleeve chamber.
 9. A device as recited in claim 8 wherein the device further comprises an O-ring disposed between the inner surface of the distal tube and the outer surface of the proximal tube.
 10. A device as recited in claim 9 wherein the device further comprises an annular ring mounted on the outer surface of the proximal tube and positioned in the sleeve chamber, the annular ring axially moveable relative to the O-ring during a pressurization of the sleeve chamber to deform the O-ring and increase a sealing force between the O-ring, the annular ring and the inner surface of the distal tube.
 11. A device as recited in claim 1 wherein the vent is formed in the shape of a labyrinth passageway.
 12. A device as recited in claim 1 wherein the launcher is man-powered.
 13. A device as recited in claim 12 wherein the launcher is a vertical bow.
 14. A device which comprises: a proximal tube formed with a lumen; a piston covering the distal end of the proximal tube; a distal tube formed with a lumen and having an open proximal end and a closed distal end; the distal tube engaged with the proximal tube to establish a compression chamber in the lumen of the distal tube between the piston and the closed distal end of the distal tube; a means for regulating an introduction of fluid into the proximal tube lumen to pressurize the compression chamber; and a launcher for generating a driving force on the proximal tube to propel the proximal tube onto a flight path with an initial relative movement between the proximal and distal tubes to compress gas in the compression chamber for use in separating the proximal and distal tubes in flight.
 15. A device as recited in claim 14 wherein the regulating means comprises a valve at the proximal end of the proximal tube to selectively pressurize a space in the lumen of the proximal tube between the valve and piston, the space being in fluid communication with the compression chamber through a vent formed in the piston.
 16. A device as recited in claim 15 wherein the piston is formed with a wall and the vent comprises a hole extending through the wall of the piston.
 17. A device as recited in claim 15 wherein the vent is formed in the shape of a labyrinth passageway.
 18. A device as recited in claim 14 wherein the proximal tube has an outer surface, the distal tube has an inner surface and the proximal tube is engaged with the distal tube to establish a sleeve chamber between the inner surface of the distal tube and the outer surface of the proximal tube.
 19. A device as recited in claim 18 wherein the proximal tube is formed with an opening to establish fluid communication between the space in the proximal tube and the sleeve chamber and the device further comprises an O-ring disposed between the inner surface of the distal tube and the outer surface of the proximal tube.
 20. A device as recited in claim 19 wherein the device further comprises an annular ring positioned in the sleeve chamber, the annular ring axially moveable relative to the O-ring during a pressurization of the sleeve chamber to deform the O-ring and increase a sealing force between the O-ring, the annular ring and the inner surface of the distal tube.
 21. A method for assembling a device, the method comprising the steps of: providing a distal tube formed with a lumen, and wherein the distal tube defines an axis and has an open proximal end and a closed distal end; covering the distal end of a proximal tube with a piston; the piston formed with a vent; engaging the distal tube with the proximal tube to provide for a back and forth axial movement of the proximal tube in the lumen of the distal tube, the proximal tube formed with a lumen and having a proximal end and a distal end; the proximal tube engaged with the distal tube; and using a valve at the proximal end of the proximal tube to selectively pressurize a space in the lumen of the proximal tube between the valve and piston, the space being in fluid communication with the distal tube lumen through the vent to establish a compression chamber therein between the piston and the closed distal end of the distal tube.
 22. A method as recited in claim 21 wherein the space and the compression chamber are pressurized to a pressure in the range of 70 to 90 psig.
 23. A method as recited in claim 21 wherein the piston is formed with a wall and the vent comprises a hole extending through the wall of the piston.
 24. A device as recited in claim 7 further comprising a friction ring mounted on the inner surface of the distal tube and positioned in contact with the outer surface of the proximal surface to prevent the distal tube from separating from the proximal tube prior to launch. 